Does Equi–Minimum Alveolar Concentration Value Ensure Equivalent Analgesic or Hypnotic Potency?

Abstract

Background Minimum alveolar concentration (MAC) has traditionally been used to compare the potency of volatile anesthetics. However, as it reflects the spinal mechanism of immobility rather than the cerebral mechanism of analgesia and hypnosis, it is doubtful that equi-MAC connotes equivalent analgesic or hypnotic potency. The level of analgesia and hypnosis can be assessed using surgical pleth index and bispectral index (BIS) values, respectively. This study was designed to compare the surgical pleth index and BIS values produced by equi-MAC of desflurane and sevoflurane in patients undergoing single-agent volatile anesthesia. Methods Eighty-nine patients were randomly allocated to two groups receiving either desflurane (n = 44) or sevoflurane (n = 45). Anesthesia was only maintained with assigned volatile anesthetic of age-corrected 1.0 MAC. Surgical pleth index values as an analgesic estimate and BIS values as a hypnotic estimate were obtained under standard tetanic stimulation. Results Post-stimulation surgical pleth index values (mean ± SD), the primary outcome, were significantly lower for the desflurane group than those for the sevoflurane group (49 ± 10 vs. 64 ± 14, difference, 15 [95% CI, 10 to 20], P < 0.001). The desflurane group showed significantly lower poststimulation BIS values (median [interquartile range]) than the sevoflurane group (36 [31 to 41] vs. 41 [38 to 47], difference, 6 [95% CI, 2 to 9], P = 0.001). Conclusions During a steady-state of 1.0 MAC, desflurane and sevoflurane did not cause similar surgical pleth index and BIS values under the standardized nociceptive stimulus. These findings suggest that equi-MAC of desflurane and sevoflurane may not ensure equivalent analgesic or hypnotic potency.

Desflurane reduces intraoperative remifentanil requirements more than sevoflurane: comparison using surgical pleth index-guided analgesia

“…Regarding the EEG measures, the equi-MAC of the two inhaled anaesthetics did not produce similar BIS and entropy values. This result is consistent with the results of previous studies, 23,31 which suggest that the effect of the two anaesthetics on the EEG at equi-MAC may be different. Regarding the haemodynamic measures, both groups showed stable haemodynamics during the surgery, with the MAP and HR maintained within ±20% of the pre-induction baseline values.…”

“…Second, this difference might have been a result of the different anaesthetic effects between the two inhaled anaesthetics. We have previously reported that sevoflurane and desflurane did not produce similar SPI and BIS under a standardised tetanic stimulation during a steady state of 1.0 MAC single-agent inhaled anaesthesia, 23 consistent with the pre-incision data of the current study. These results suggest that the inhaled anaesthetic equivalence of the effects on the spinal cord might not be equivalent to that on the cerebrum.…”

“…20e22 Therefore, it is unclear whether equi-MAC doses of different inhaled anaesthetics ensure equivalent hypnotic or antinociception levels. 23 The authors hypothesised that sevoflurane and desflurane at equi-MAC would not show a similar opioid consumption during SPI-guided analgesic administration. This study aimed to compare intraoperative remifentanil requirements during 1.0 MAC sevoflurane and desflurane anaesthesia in patients undergoing laparoscopic cholecystectomy under SPI-guided remifentanil administration.…”

Hypnotic potency differs between desflurane and sevoflurane

“…They conducted study under no surgical stimulation. Recent two trials provided further information under uniform stimulation [2,3]. One study compared BIS and surgical pleth index (SPI) between desflurane and sevoflurane under a uniform tetanic stimulation by nerve stimulator [3] and found that both indexes are significantly lower in desflurane group, suggesting that the cerebral effect of volatile agents may differ at 1 MAC.…”

“…Recent two trials provided further information under uniform stimulation [2,3]. One study compared BIS and surgical pleth index (SPI) between desflurane and sevoflurane under a uniform tetanic stimulation by nerve stimulator [3] and found that both indexes are significantly lower in desflurane group, suggesting that the cerebral effect of volatile agents may differ at 1 MAC. Another study compared the remifentanil requirement to maintain an equal SPI under the same surgical stimulation of dissection of the gall bladder between desflurane and sevoflurane [2].…”